Please indicate if the statements below are true $($T$)$ or false $($F$).$

$$Differential relays can serve as the primary protection devices for internal faults of buses.

$$Differential relays use the ratio between voltage and current for fault detection.

$$Impedance relays use the angle difference between voltage current for fault detection.

$$Directional relays use both voltage and current measurements for fault detection.

$$Potential transformers may have poor measurement accuracy due to saturation.

$$Three$-$phase balanced fault is the most popular type of fault in real$-$world power systems.

$$The operation time of the backup relay should be determined based on the operation time of the primary relay, the relay coordination time interval, and the circuit breaker clearing time.

$$In high$-$voltage transmission systems, fuses and reclosers are frequently used and coordinated to provide primary and backup protections.

$$If differential relays are used to protect three$-$phase power transformers with Y$-$Delta connection, the current transformer on the Y side of the three$-$phase power transformer should be connected in Y$,$ and the current transformer on the Delta side of the three$-$phase power transformer should be connected in Delta.

$$Va $=$ Vb $=$ Vc $=1<30$ pu is a zero sequence three$-$phase voltage set.